Target shoppers nationwide will now be able to make purchases on Google Express, after a successful test on the platform in California and New York, the company announced Thursday.

The big-box retailer is among several that are deepening their relationships with Google's voice-activated shopping platform in a battle for market share against Amazon's Alexa-enabled devices.

Target announced that by 2018, the retailer's credit card holders will be able to link their cards and save 5 percent when shopping Target via Google Express. Shoppers will also have an option in 2018 to link their Target.com accounts to Google for a more personalized experience, similar to what Wal-Martannounced earlier this year.

For example, a shopper might say to the Google Assistant on Google Home: "Google, order me shampoo." If that shopper has accounts linked both to Target.com and Walmart.com, but he or she orders shampoo more frequently from Target, Google will pull results from Target's website.

Target's product assortment on Google Express will include anything in a typical Target store, which will serve as fulfillment centers. In 2018, shoppers will be able to pick up their Target purchases made via Google Express at Target stores, should they want to forgo waiting on a shipment.

"Target and Google teams are working on the next chapter, building experiences that digitally replicate the joy of shopping a Target store to discover stylish and affordable products," said Target's chief information and digital officer, Mike McNamara.

In tandem with Target's roll-out on Thursday, Google has also unveiled plans to grow the number of ways customers can use the Google Assistant.

Until now, the voice platform has been available on the Google Home and on Android TVs. Soon, it will launch on iPhones and Android phones, so customers can order items, using voice, while mobile.

"At Google, we are focused on continued innovation and making Google Express a platform to help retailers like Target offer consumers a high quality seamless, end-to-end shopping experience," said Daniel Alegre, Google's president of retail and shopping.

Earlier this month, Wal-Mart announced that shoppers could browse more than 2 million of the big-box retailer's items via Google Express. Wal-Mart was also giving shoppers coupons if they bought a Google Home or Google Home Mini, and linked their Walmart.com accounts to Google Express.

Bulking up against internet giant Amazon, more and more retailers have been touting their partnerships with Google and encouraging shoppers to buy Google devices. To be sure, the penetration of Google Home devices in American households is still less than that of Amazon's Echo devices.

Companies, like Wal-Mart and Target are still finding ways to grow with Google, promising more to come.

"Next year, we will also leverage our 4,700 U.S. stores and our fulfillment network to create customer experiences that don't currently exist within voice shopping anywhere else," Marc Lore, head of Wal-Mart's U.S. e-commerce business, said in a blog post.

This will include using voice command to pick up orders in store and using voice shopping to purchase fresh groceries, he said.

Target likewise initially won't offer fresh groceries via Google Express, a representative told CNBC. But it has plans to grow in other areas with voice-enabled shopping, like apparel, home and beauty, the company said.

Today, for example, shopping for dry goods like coffee and paper towels through voice-enabled devices is more easily accomplished than picking out an outfit, where there are many more factors involved. But Target is aiming to perfect the response to shoppers telling the Google Assistant, "Google, find me a red dress."